The present invention relates to semiconductor devices and more particularly to III-nitride heterojunction semiconductor devices.
Conventional III-nitride power heterojunction semiconductor devices include at least two power electrodes and a gate arrangement disposed therebetween all disposed on one surface of a semiconductor die. Consequently, conventional III-nitride heterojunction semiconductor devices are typically lateral conduction devices.
In many applications, including power applications, two or more devices need to be integrated. Integration of lateral conduction devices results in relatively complex routing and the like which results, among other drawbacks, parasitic drain to source capacitance.
In accordance with the invention, the substrate of a III-nitride heterojunction semiconductor device is used as a third access path to a set of active contacts, rather than simply shorting the substrate to a source or drain, or just floating.
More specifically, in a device according to the present invention a third power electrode residing on a top surface of the device is connected vertically down to the substrate using a metal plug or via. The third power electrode may be disposed between the two other power electrodes.
The third electrode may be a drain electrode while the other two electrodes may be the first source electrode and the second source electrode. Thus, the electrodes may be arranged in the sequence source 1, drain, source 2, or, in the case of a half bridge arrangement, source 1, source 2, drain, source 2, source 2, source 1, source 2, drain, and so on.
In a device according to the present invention, the basic idea is to use the vertical direction through the device to facilitate the integration of multiple switches, which results in the following:                ease of metal routing;        reduction of high voltage metal cross-overs;        reduction of drain to source capacitance from those cross-overs; and        device symmetry with respect to substrate in a common drain configuration.        
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.